Support missing SNIMissingWarning in tests (#6336)

tests/__init__.py

@@ -2,9 +2,13 @@
 
 import warnings
 
-from urllib3.exceptions import SNIMissingWarning
+try:
+    from urllib3.exceptions import SNIMissingWarning
 
-# urllib3 sets SNIMissingWarning to only go off once,
-# while this test suite requires it to always fire
-# so that it occurs during test_requests.test_https_warnings
-warnings.simplefilter("always", SNIMissingWarning)
+    # urllib3 1.x sets SNIMissingWarning to only go off once,
+    # while this test suite requires it to always fire
+    # so that it occurs during test_requests.test_https_warnings
+    warnings.simplefilter("always", SNIMissingWarning)
+except ImportError:
+    # urllib3 2.0 removed that warning and errors out instead
+    SNIMissingWarning = None

tests/test_requests.py

@@ -48,6 +48,7 @@
 from requests.sessions import SessionRedirectMixin
 from requests.structures import CaseInsensitiveDict
 
+from . import SNIMissingWarning
 from .compat import StringIO
 from .utils import override_environ
 
@@ -974,6 +975,10 @@ def test_http_with_certificate(self, httpbin):
         r = requests.get(httpbin(), cert=".")
         assert r.status_code == 200
 
+    @pytest.mark.skipif(
+        SNIMissingWarning is None,
+        reason="urllib3 2.0 removed that warning and errors out instead",
+    )
     def test_https_warnings(self, nosan_server):
         """warnings are emitted with requests.get"""
         host, port, ca_bundle = nosan_server